Determination of troponin I release after CABG surgery
Joseph Noora1, Christopher Ricci, Deborah Hastings
1McMaster University, Hamilton, Ontario, Canada.
Insights
Coronary artery bypass graft surgery elevates troponin I levels, peaking postoperatively. Preoperative troponin I may predict elevated postoperative levels without myocardial infarction.
Area of Science:
- Cardiology
- Cardiac Surgery
- Biomarkers
Background:
- Troponin I is a key biomarker for diagnosing myocardial infarction (MI).
- The pattern and diagnostic utility of troponin I elevation after coronary artery bypass graft (CABG) surgery are not well-established.
- This study investigates troponin I kinetics in patients undergoing urgent CABG.
Purpose of the Study:
- To assess the timing and magnitude of troponin I elevation following urgent CABG.
- To determine if troponin I elevation patterns differ between patients with and without perioperative myocardial infarction (PMI).
- To identify predictors of elevated postoperative troponin I levels.
Main Methods:
- Prospective study of 50 patients undergoing urgent isolated-CABG with cardiopulmonary bypass.
- Serial measurements of troponin I, CK, and CK-MB preoperatively and at multiple postoperative time points (7h, 14-18h, 30-48h, day 4).
- Perioperative MI (PMI) defined by ECG and/or CK-MB criteria.
Main Results:
- 12% of patients (6/50) met criteria for PMI.
- In patients without PMI, troponin I peaked at 7 hours post-op (mean 20.97 µg/L).
- Patients with PMI had significantly higher troponin I levels at 7 hours post-op (mean 46.85 µg/L).
- Preoperative troponin I was the only significant predictor of peak postoperative troponin I in patients without PMI.
Conclusions:
- CABG surgery causes significant troponin I elevation, often exceeding diagnostic thresholds for MI, without actual MI occurrence.
- Troponin I levels typically peak during the second postoperative day.
- Elevated preoperative troponin I may indicate higher postoperative troponin I levels in patients without PMI, suggesting non-ischemic causes.
Background:
Troponin I is used to diagnose myocardial infarction (MI). Its use and pattern of elevation is not well defined in coronary artery bypass graft (CABG) surgery. This study assessed the timing of troponin I elevation in patients undergoing urgent CABG.
Method:
Patients undergoing urgent isolated-CABG with cardiopulmonary bypass were studied prospectively. Blood samples were taken to measure CK, CK-MB, and troponin I: preoperatively, 7 hours postoperatively, 14 to 18 hours postoperatively, 30 to 48 hours postoperatively, and on postoperative day 4. Electrocardiograms and in-hospital course were recorded. Perioperative MI (PMI) was defined by either (i) ECG criteria of new Q-waves in the presence of CK-MB elevation >50 microg/L or (ii) CK-MB > 100 microg/L.
Results:
Of the 50 patients studied, 6 met the criteria for PMI (12%); 2 by criteria (i) and 4 by criteria (ii). In patients not meeting the criteria for MI the troponin I level peaked at 7 hour post-op with a mean of 20.97 microg/L (95% CI, 17.11 to 24.83). At this time, patients who met the criteria for MI had a mean troponin I level of 46.85 microg/L (95% CI, 36.40 to 57.30). Of variables investigated for the 44 patients who did not meet MI criteria, only preoperative troponin I level impacted peak postoperative troponin I.
Conclusions:
CABG elevates troponin I far beyond current diagnostic benchmarks without the clinical occurrence of a MI and appears to peak during the second postoperative day. An elevated preoperative troponin I may predict an elevated peak postoperative troponin I in patients who do not have a PMI.
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